Sorry to be a bother. I work for oracle and use this as a tool for troubleshooting x86, oel, and other os issues.
I am running a quad core phenom 955 am3 with 6 GB ddr3 memory(3x2). My host system is windows xp pro 64bit. When I run virtual box and the guests combined memory usage(not allocation) exceeds around 1 GB, I get a severity non-fatal error, with an error-id of HostMemoryLow.
If I put 12 GB of ram in the system(2x4,2x2). I get the same error when the combined used memory in the guests exceeds a little over 3GB of ram.
I have run memtest on the system multiple times. I can allocate the memory in vmware player and everything is happy.
I love virtualbox - it works fine on my mac, but my mac doesn't have the horsepower of my desktop.
This has been present since 3.1.4 at least. I have seen similar posts as well.

This is still present and keeping me from using virtualbox - I have seen posts with this similar issue for the past couple of years. It appears to be a bug that has gone unfixed and should be addressed. Any suggestions - I can use vmware player and it works fine, but that limits what I can do.